MOLA-MOLA / SUN FISH

The ocean sunfish, Mola mola, or common mola, is the heaviest known bony fish in the world. It has an average adult weight of 1 tonne (2,200 lbs). The species is native to tropical and temperate waters around the globe.

It resembles a fish head with a tail, and its main body is flattened laterally. Sunfish can be as tall as they are long when their dorsal and ventral fins are extended.

Sunfish live on a diet that consists mainly of jellyfish. Because this diet is nutritionally poor, they consume large amounts in order to develop and maintain their great bulk.

Females of the species can produce more eggs than any other known vertebrate. Sunfish fry resemble miniature puffer fish, with large pectoral fins, a tail fin and body spines uncharacteristic of adult sunfish.

The ocean sunfish resembles a fish head with a tail. Its caudal fin is replaced by a rounded clavus, creating the body's distinct shape. The main body is flattened laterally, giving it a long oval shape when seen head-on.

The pectoral fins are small and fan-shaped. However, the dorsal fin and the anal fin are lengthened, often making the fish as tall as it is long. Specimens up to 3.2 meters (10.5 ft) in height have been recorded

The ocean sunfish has an average length of 1.8 meters (5.9 ft), and an average weight of 1,000 kilograms (2,200 lb), although individuals up to 3.3 meters (10.8 ft) in length 4.2 m (14 ft) across the fins and weighing up to 2,300 kilograms (5,100 lb) have been observed.

Sunfish are pelagic and swim at depths of up to 600 meters (2,000 ft). Contrary to the general perception that sunfish spend much of their time basking at the surface, research suggests that adult M. mola actually spend a large portion of their lives submerged at depths greater than 200 meters (700 ft), occupying both the epipelagic and mesopelagic zones.

They usually stay in water warmer than 10 °C (50 °F). In fact, prolonged periods spent in water at temperatures of 12 °C (53 °F) or lower can lead to disorientation and eventual death. Researchers theorize that the basking behavior at the surface, in which the sunfish swims on its side presenting its largest profile to the sun, may be a method of "thermally recharging" following dives into deeper, colder water.

Sunfish are usually found alone, but occasionally in pairs or in large groups while being cleaned. They swim primarily in open waters, but are sometimes seen near kelp beds taking advantage of resident populations of smaller fish which remove ectoparasites from their skin.

Because sunfish must consume a large volume of prey, their presence in a given area may be used as an indicator of nutrient-rich waters where endangered species may be found.